One of the world's most useful sources of energy is crude oil, derived from subterranean formations. When crude oil arrives at the earth's surface it is typically in the form of a water-in-oil mixture. That is, crude oil invariably has associated water that must be separated before the oil component can be efficiently refined into useful commercially acceptable products.
A common technique for improving the effectiveness of oil/water separation is by use of coalescence—that is a technique of joining together smaller into larger water droplets that are more readily separated from the mixture. As water droplet size increases, the dynamics of gravitational separation improve. One method of augmenting coalescence of water droplets is by subjecting the mixture to an electric field. Oil, being a non-polar fluid, acts as a dielectric and water droplets, being polar, when subjected to an electric field are coalesced. Coalescence is usually practiced by establishing an electric field between electrodes and passing an oil-in-water mixture through the electric field. Since water is slightly polar, water droplets become polarized by the electric field. Polarized droplets are attracted to each other and move into and coalescence with each other. Larger droplets tend to gravitate downwardly within the mixture and the oil, having portions of the water removed therefrom, tend to gravitate upwardly within the mixture.
Much work has been done in the area of electrostatic coalescence of a mixture to augment separation of oil and water components. Background information relating to the inventive subject matter contained herein can be obtained from the following United States patents:
Pat. No.InventorTitle1,116,299Laird et al.Process of treating petroleum emulsions1,276,387McKibbenMethod of separating associated liquids1,838,931FisherApparatus for converting commercial frequency circuits into highfrequency circuits2,120,932DillonHigh frequency induction dehydrator2,849,395WintermuteMethod and apparatus for electrical separation of emulsions3,772,180PrestridgeElectric treater3,839,176McCoyMethod and apparatus for removing contaminants from liquids3,847,775PrestridgeProcess for electrical coalescing of water4,126,537PrestridgeMethod and apparatus for separation of fluids with an electric field4,161,439Warren et al.Apparatus for application of electrostatic fields to mixing andseparating fluids4,200,516PopeElectrostatic coalescing system4,204,934Warren et al.Process for application of electrostatic fields to mixing andseparating fluids4,224,124PopeElectrostatic coalescing system4,283,290DaviesPurification utilizing liquid membrane with electrostatic coalescence4,290,882DempseyElectrostatic separation of impurities phase from liquid-liquidextraction4,308,127PrestridgeSeparation of emulsions with electric field4,400,253PrestridgeVoltage control system for electrostatic oil treater4,415,426Hsu et al.Electrodes for electrical coalescence of liquid emulsions4,417,971Ferrin et al.Circuit for maintaining the strength of an electrostatic field generatedin a fluid mixture of varying dielectric strength4,469,582Sublette et al.Electrically enhanced inclined plate separator4,479,161Henrich et al.Switching type driver circuit for fuel injector4,581,119Rajani et al.Apparatus for separating a dispersed liquid phase from a continuousliquid phase by electrostatic coalescence4,581,120SubletteMethod and apparatus for separating oilfield emulsions4,601,834Bailes et al.Settling of liquid dispersions4,606,801Prestridge et al.Electrostatic mixer/separator4,702,815Prestridge et al.Distributed charge composition electrodes and desalting system4,747,921BailesLiquid-liquid contacting4,767,515Scott et al.Surface area generation and droplet size control in solvent extractionsystems utilizing high intensity electric fields4,804,453Sublette et al.Resolution of emulsions with multiple electric fields5,147,045Chi et al.Particulate separations by electrostatic coalescence5,411,651Yamaguchi et al.Method for electrostatic liquid/liquid contactor5,421,972Hickey et al.Process and apparatus for removing soluble contaminants fromhydrocarbon streams5,464,522MacEdmondsonElectrostatic oil emulsion treating method and apparatus5,543,027Yamaguchi et al.Apparatus for electrostatic liquid/liquid contactor5,565,078Sams et al.Apparatus for augmenting the coalescence of water in a water-in-oilemulsion5,575,896Sams et al.Method and apparatus for oil/water separation using a dual electrodecentrifugal coalescer5,643,431Sams et al.Method for augmenting the coalescence of water in a water-in-oilemulsion5,824,203RemoMethod and means for changing characteristics of substances6,010,634Sams et al.System and method for separating mingled heavier and lightercomponents of a liquid stream6,113,765Wagner et al.Methods for enhanced resolution of hydrocarbon continuousemulsions or dispersions with conductivity modifiers6,860,979SamsDual Frequency Electrostatic Coalescence